1. Field of the Invention
The present invention relates to intravascular radiotherapy source ribbon assemblies, and more particularly to unidummy intravascular radiotherapy source ribbon assemblies comprising non-radioactive materials of varying radiopacity for ascertaining the proper position for the placement of radioactive materials within the vasculature.
2. Discussion of the Related Art
Percutaneous transluminal coronary angioplasty (PTCA) is a therapeutic medical procedure used to increase blood flow through an artery and is the predominant treatment for coronary vessel stenosis. The increasing popularity of the PTCA procedure is attributable to its relatively high success rate and its minimal invasiveness compared with coronary by-pass surgery. Patients treated utilizing PTCA; however, may suffer from restenosis. Restenosis refers to the re-narrowing of an artery after a successful angioplasty procedure. Restenosis usually occurs within the initial six months after an angioplasty. Early attempts to alleviate the effect of restenosis included repeat PTCA procedures or by-pass surgery, with attendant high cost and added patient risk.
More recent attempts to prevent restenosis by use of drugs, mechanical devices, and other experimental procedures have limited long term success. Stents, for example, dramatically reduce acute reclosure and slow the effects of smooth muscle cell proliferation by enlarging the maximal luminal diameter, but otherwise do nothing substantial to slow the proliferative response to the angioplasty induced injury.
Restenosis is now believed to occur at least in part as a result of injury to the arterial wall during the lumen opening angioplasty procedure. In some patients, the injury initiates a repair response that is characterized by hyperplastic growth of the vascular smooth muscle cells in the region traumatized by the angioplasty. Intimal hyperplasia or smooth muscle cell proliferation narrows the lumen that was opened by the angioplasty, regardless of the presence of a stent, thereby necessitating a repeat PTCA or use of other procedures to alleviate the restenosis.
Recent studies indicate that intravascular radiotherapy (IRT) has promise in the prevention or long-term control of restenosis following angioplasty. Intravascular radiotherapy may also be used to prevent or delay stenosis following cardiovascular graft procedures or other trauma to the vessel wall. Proper control of the radiation dosage, however, appears to be important to inhibit or substantially arrest hyperplasia without causing excessive damage to healthy tissue. Underdosing will result in inadequate inhibition of smooth muscle cell hyperplasia, or possibly even exacerbation of hyperplasia and resulting restenosis.
Radiation therapy may also be utilized in the treatment of other diseases such as cancerous and non-cancerous tumors or other proliferative normal tissue disorders. In this type of therapy, the ultimate aim is to destroy the malignant tissue without causing excessive radiation damage to nearby healthy, and possibly vital tissue. This is difficult to accomplish because of the proximity of malignant tissue to healthy tissue.
Brachytherapy is a form of radiation treatment in which an ionizing radiation source, for example, an intravascular radiotherapy source ribbon assembly, is placed into or adjacent to a tumor or stenotic lesion. Although any number of radioactive substances and/or radioactive sources may be utilized in brachytherapy, Iodine-125 is currently a good candidate isotope for vascular brachytherapy. Iodine-125 has been used as a liquid or immobilized onto a variety of surfaces for diagnostic and therapeutic purposes. It has already been fashioned into a variety of shapes and used clinically for cancer treatment as briefly described above. One standard method for immobilizing Iodine-125 on to a solid surface is through electroplating. Currently, Iodone-125 is immobilized onto the surface of solid silver wires for a very secure bond and because silver is radiopaque and thus is easily seen under X-ray fluoroscopy. It is important that a radiopaque material such as silver is utilized as a substrate for the radioactive substance because proper positioning of the radioactive substance is critical to the success of any brachytherapy procedure. In order to ensure that the proper radiation dosage is delivered to the stenotic lesion or abnormal cell growth with minimal exposure of healthy tissue, precise placement of the radioactive substance is required. Accordingly, there is a need for a device that has substantially the same profile as an intravascular radiotherapy source ribbon assembly, but rather than containing radioactive materials, comprises the same substrate as well as markers of differing radiopacity to effectively map out the area or region under treatment.
The unidummy intravascular radiotherapy source ribbon assembly of the present invention provides a means for overcoming the difficulties associated with the devices currently in use as briefly described above.
In accordance with one aspect, the present invention is directed to a unidummy intravascular radiotherapy source ribbon assembly. The unidummy intravascular radiotherapy source ribbon assembly comprises a container defining a cavity and a core disposed within the cavity of the container. The core comprises one or more non-radioactive sections having a first radiopacity and one or more sections having a second radiopacity disposed between the one or more sections having a first radiopacity.
In accordance with another aspect, the present invention is directed to a unidummy intravascular radiotherapy source ribbon assembly. The unidummy intravascular radiotherapy source ribbon assembly comprises a container defining a cavity and a core disposed within the cavity of the container. The core comprises one or more non-radioactive sections having a first radiopacity and one or more non-radioactive sections having varying radiopacities different from the first radiopacity disposed between the one or more sections having a first radiopacity.
In accordance with another aspect, the present invention is directed to a method for positioning an intravascular radiotherapy source ribbon assembly at a treatment site. The method comprises introducing a unidummy intravascular radiotherapy source ribbon assembly having a core comprising one or more non-radioactive sections having a first radiopacity and one or more non-radioactive sections having a second radiopacity disposed between the one or more sections having a first radiopacity to the treatment site, subjecting the treatment site to X-ray fluoroscopy, and determining the proper position for the one or more non-radioactive sections having a first radiopacity relative to the treatment site.
The unidummy intravascular radiotherapy source ribbon assembly of the present invention comprises a combination of one or more markers interspersed between sections of material comprising the substrate onto which the radioactive material is disposed. The sections of material comprising the substrate have a certain radiopacity, and the one or more markers have a different radiopacity, preferably lower than the substrate material. The unidummy intravascular radiotherapy source ribbon assembly has substantially the same profile and characteristics as a xe2x80x9chotxe2x80x9d or radioactive intravascular radiotherapy source ribbon assembly. In having substantially the same profile and characteristics, the unidummy assembly may be utilized to ensure that the path through the vasculature or other pathway in the body is free of obstructions or open to the site of radiation delivery without exposing the patient to unnecessary radiation. In addition, to achieve the best possible results, the radioactive source is preferably positioned to deliver radiation to the entire stenotic lesion or tumor and not to the surrounding or adjacent healthy tissue. Accordingly, the unidummy assembly may be utilized to properly size and position the radioactive seeds. Essentially, since the unidummy assembly utilizes sections of the material comprising the substrate onto which the radioactive material is disposed along with one or more markers having different radiopacities, the exact positioning for the xe2x80x9chotxe2x80x9d intravascular radiotherapy source ribbon assembly may be determined without having to utilize the xe2x80x9chotxe2x80x9d intravascular radiotherapy source ribbon assembly. Mapping the treatment site with the unidummy assembly thereby minimizes unnecessary radiation exposure.
The unidummy intravascular radiotherapy source ribbon assembly of the present invention provides for the safe and effective determination of the precise position coordinates for the xe2x80x9chotxe2x80x9d intravascular radiotherapy source ribbon assembly as well as determining if the path thereto is free from obstruction. Since the unidummy assembly is configured and has the same profile as the xe2x80x9chotxe2x80x9d assembly, it is easy for the doctor or other health care professional to utilize. In addition, since the xe2x80x9chotxe2x80x9d intravascular radiotherapy source ribbon assembly is essentially identical to the unidummy assembly, the doctor or other health care professional may easily make the transition from one assembly to the other.